For a facility that has not been the subject of a conversion and that has residents who are not parties to continuing care agreements, the provider shall calculate the amount of operating reserves required under § 10–420 of this subtitle based on the pro rata proportion of the net operating expenses as specified under subsection (b) of this section. The pro rata proportion of the net operating expenses equals the number of units in the facility for which the Department has issued a certificate of registration divided by the total number of accommodations in the facility multiplied by the net operating expenses for the most recent fiscal year for which a certified financial statement is available.